the Bento growth platform

Why Are My Emails Getting Blocked?

Thoughts by Gracija Atanasovska • Writer Bento

At the beginning of every email campaign, there are high hopes for the highest delivery rates, open rates, and engagement. The reality is, however, that some emails might get blocked, leaving you wondering why this happened in the first place.

The reasons for this vary, so let’s go over them and explain how to prevent this from happening again.

Email Delivery Errors Explained

As part of your email marketing campaign, you send thousands of emails per day. Most of those emails will reach their destination, but there are, in fact, four ways in which your emails may end up:

  • Delivered: this means that the server of the recipient has accepted the message and it should end up either in their inbox or their spam/junk folder;

  • Deferred: in this scenario, the recipient’s server delayed accepting your message for some reason. Usually, this happens because too many messages have been sent from the sender’s address in a short amount of time;

  • Bounced: when an email bounces, it means that the recipient’s server has denied the message being sent and that it could not be delivered to the recipient’s inbox;

  • Blocked: an email blocked by the server means that it was temporarily denied access to the inbox of the recipient. It indicates a problem with the sender’s address and sender’s message content and not the ones of the recipient.

Next, I want to talk a bit more about what each of these events signifies and why it happens. This will help you to have a clearer image of your email delivery practices and performance.

Delivered Email Messages

People often think that “message delivered” automatically means that the email has landed straight into the recipient’s inbox. Well, that’s not entirely the case.

A delivered message actually means that the recipient’s server has accepted the message from the sender. However, once this happens, the fate of the message is to be decided further by the receiving server. Most frequently, there are two possible outcomes: the server either delivers the message to the recipient’s inbox or to their spam/junk folder. Sometimes, albeit quite rarely, it also happens that the receiving server just drops the message, basically deleting it on its own. In this scenario, the recipient won’t be able to find the message no matter where they look in their email folders.

How Does the Server Know Where to Place the Message?

The answer, almost without exception, lies in the sender’s sending reputation as well as the content of the message.

If the sender experiences a high amount of spam complaints from their recipients, or if the email providers know they send content that generates high rates of spam complaints, it’s highly likely that the emails will reach the recipient's spam/junk folders instead of their inboxes.

So, as you can see, getting your emails delivered is only part of the story. It’s also important where they end up.

Deferrals or Deferred Emails

When an email is being deferred it means that the recipient’s server has temporarily stalled or delayed the delivery.

Deferrals are usually pretty benign. It doesn’t mean that your email won’t be delivered to the intended address - it’s just a temporary delay and it usually resolves itself in a couple of minutes or hours.

Usually, the sender’s servers will continue to try and deliver the message for up to 72 hours, and if it doesn’t resolve itself by then, it will probably turn into a block.

Why Do Deferrals Happen?

Deferrals usually happen because of too many emails being sent from the sender’s address. When this happens, email providers want to prevent their servers from overflooding and try to check for any potential spam messages. Your emails may also be deferred if the email providers have received too many spam complaints about your email address, or the server had some temporary technical issues when the emails were being sent.

Bounced Emails

Email bounces happen when an email message cannot be delivered to the intended address and it signifies an issue with the recipient’s server and address. There are two types of bounces - hard and soft bounces. Why Do Emails Bounce? Soft bounces are similar to deferrals, and the issue is usually temporary, like a full inbox or the recipient being offline, while hard bounces are more serious and they signify a permanent rejection of the sent email. Hard bounces are usually a result of a fake or invalid email address of the recipient, but they also sometimes happen if your email address has been blocked.

Blocked Emails

When an email is blocked it means that it has been temporarily rejected (non-permanent rejection) by the recipient’s server. But unlike email bounces, emails get blocked because of a fault with the sender, more precisely with their email message. So it doesn’t have anything to do with the recipient but rather with the sender and their message content.

Email Blocked By Server - Why Does it Happen?

There are a variety of reasons why your emails get blocked. Let’s take a look at what the most common ones are and what you can do about them.

Your Email Content Looks Like Spam

Usually, email providers recognize spam through stylistic and contextual filters. This means that your content may be deemed spam if your subject lines are written in all caps if the words in the subject line are misspelled, if the message content contains text with large font size or too much use of bold, or if you sound too promotional or too in-your-face sale-like.

Moreover, you should pay attention to the links you put in the body of the email because they can also be a large factor in determining whether you get blocked or not. The most important thing is to ensure that the links are secure and trustworthy.

Your Email Volume Has Suddenly Increased

A sudden, abrupt change in email volume may also be the reason why your emails get blocked by a server.

A sudden volume increase is a potential red flag for email providers which is often considered spammer behavior. That’s why it’s best to gradually increase the number of emails you send per day and per month.

If your email volume increases in a short amount of time, make sure that you have the right security to back it up. Also, consider getting a dedicated IP address so you have the infrastructure for a high volume of messages as well as more control of the whole process of sending emails.

Your Sender’s IP Address Was Placed on a Suspended List

Email blocks can also happen if your address has been blacklisted. This can happen if you’re using a shared IP with addresses that have poor sender reputation or phishing attacks in which hackers use your IP address to send spam and malware emails to recipients.

If your address has been blacklisted, you’ll notice a higher amount of hard-bounced emails and spam complaints than usual. When this happens, you have to act quickly so you don’t damage your open rates and overall sender reputation even more.

You have to check which provider is blocking your IP and regularly clean your email lists. For more detailed info on what to do if you’ve been list denied or added to a black list, check my article on email reputation and blacklists.

You’re Sending to a Large Number of Invalid Addresses

If you’re constantly sending emails to too many invalid addresses, you risk getting your emails blocked and being considered a spammer. What’s more - you even risk stumbling upon a spam trap, which can damage your IP reputation and get your IP blacklisted.

So what can you do about it? Well, first of all - clean your lists regularly and practice list segmentation. Look out for misspelled emails, emails with typos, emails you haven’t engaged with in a while, and so on.

Also, don’t shy away from using the double-opt-in option to ensure that the email addresses customers use during signup are real and they want to receive your emails.


As you can see, there are various paths your emails can take once you send them on their way. As there are various ways of them not ending up where you want them to be. Emails getting blocked is nothing to be too worried about, although it is smart to always be on the lookout so you can prevent causing even bigger damage to your IP and sender reputation in the long run.